Composted versus Raw Olive Mill Waste as Substrates for the Production of Medicinal Mushrooms: An Assessment of Selected Cultivation and Quality Parameters

Abstract

Two-phase olive mill waste (TPOMW, “alperujo”) is a highly biotoxic sludge-like effluent of the olive-oil milling process with a huge seasonal production. One of the treatment approaches that has so far received little attention is the use of TPOMW as substrate for the cultivation of edible mushrooms. Fifteen fungal strains belonging to five species (Basidiomycota), that is, Agrocybe cylindracea, Pleurotus cystidiosus, P. eryngii, P. ostreatus, and P. pulmonarius, were evaluated for their efficacy to colonize media composed of TPOMW, which was used either raw or composted in mixtures with wheat straw in various ratios. Qualified strains exhibited high values of biological efficiency (e.g., 120–135% for Pleurotus spp. and 125% for A. cylindracea) and productivity in subsequent cultivation experiments on substrates supplemented with 20–40% composted TPOMW or 20% raw TPOMW. Only when supplementation exceeded 60% for raw TPOMW, a negative impact was noted on mushroom yields which could be attributed to the effluent's toxicity (otherwise alleviated in the respective composted TPOMW medium). Earliness and mushroom size as well as quality parameters such as total phenolic content and antioxidant activity did not demonstrate significant differences versus the control wheat-straw substrate. The substrates hemicellulose content was negatively correlated with mycelium growth rates and yields and positively with earliness; in addition, cellulose: lignin ratio presented a positive correlation with mycelium growth and mushroom weight for A. cylindracea and with earliness for all species examined. TPOMW-based media revealed a great potential for the substitution of traditional cultivation substrates by valorizing environmentally hazardous agricultural waste.

Pleurotus spp. Cultivation on Different Agri-Food By-Products: Example of Biotechnological Application

“…Similarly, Zervakis, et al [49] evaluated the use of two-phase olive mill wastes (TPOMWs) in the growth substrates of different Pleurotus species. When composted media were used the authors obtained a better yield, especially at low TPOMWs concentrations (20-40% for composted media and 20% for raw TPOMWs): the composting process, in fact, leads to a detoxification of the original material.…”

Comparative Examination of the Olive Mill Wastewater Biodegradation Process by Various Wood-Rot Macrofungi

“…For example, the use of microorganisms could result in both the detoxification of the effluent and the generation of value-added products, for example, xanthan gum, citric acid, ethanol, antioxidants, polyhydroxyalkanoates, b-glucan, lipase, single cell oil, and edible biomass [8–18]. …”

Cultivation of three medicinal mushroom species on olive oil press cakes containing substrates

“…Hindered mycelia growth during incubation period as well as decrease of fruiting bodies yield on OOPC containing substrates could be the consequence of polyphenols contained in OOPC (Lakhtar et al, 2010;Zervakis et al 2013). Beside polyphenolic compounds, a low porosity of OOPC and consequently lower substrate aeration and low water retaining capacity could be the reason for slower mycelial growth and lowered yields of fruiting bodies.…”

“…On the other hand fungal species and strains ability to utilize OOPC, or exposition to higher content of polyphenolic compounds in the substrate could have a significant influence on fruiting body yields. Strain characteristics tend to strongly influence mycelial growth as well as quantity and quality of produced fruiting bodies (Diehle and Royse, 1986;Royse and Bahler, 1986 (Zervakis et al, 2013).…”

“…It is well known that mushrooms can be cultivated on broad assortment of organic matter, including sawdust, straw, weeds, husks, compost and others. There were also reports of successful OOPC usage as a mushroom cultivating media (Soler-Rivas et al, 2006;Ruiz-Rodriguez et al, 2010;Zervakis et al, 2013).…”